Alterations in the structural and functional states of chromatin, mainly determined by post-translational modification of histone components, are involved in the pathogenesis of a variety of diseases. The enzymatic processes governing these post-translational modifications on the nucleosomes have become potential targets for the so-called epigenetic therapies (Portela, A. et al. Nat. Biotechnol. 2010, 28, 1057-1068).
The discovery of an increasing number of histone lysine demethylases has highlighted the dynamic nature of the regulation of histone methylation, a key chromatin modification that is involved in eukaryotic genome and gene regulation. Histone lysine demethylases represent attractive targets for epigenetic drugs, since their expression and/or activities are often misregulated in cancer (Varier, R. A. et al. Biochim. Biophys. Acta. 2011, 1815, 75-89). A lysine can be mono-, di-, and tri-methylated and each modification, even on the same amino acid, can exert different biological effects.
Histone lysine demethylases exert their activity through two different type of mechanism (Anand, R. et al. J. Biol. Chem. 2007, 282, 35425-35429; Metzger, E. et al. Nat. Struct. Mol. Biol. 2007, 14, 252-254). While the Jumonji domain-containing histone demethylases, which are iron and 2-oxoglutarate dependent oxygenases, act on mono-, di- and trimethylated lysines, the flavin-dependent (FAD) histone demethylases catalyse the cleavage of mono and dimethylated lysine residues. Currently, two FAD dependent demethylases have been identified: LSD1, also known as KDM1A, and LSD2, also known as KDM1B. (Culhane, J. C. et al. Curr Opin Chem Biol 2007, 11, 561-568, Ciccone, D. N. et al. Nature 2009, 461, 415-418).
KDM1A is a constituent in several chromatin-remodeling complexes and is often associated with the co-repressor protein CoREST. KDM1A specifically removes the methyl groups from both mono- and di-methyl Lys4 of histone H3, which is a well-characterized gene activation mark.
KDM1A represents an interesting target for epigenetic drugs as supported by data related to its over-expression in solid and hematological tumors (Schulte, J. H. et al. Cancer Res. 2009, 69, 2065-2071; Lim, S. et al. Carcinogenesis 2010, 31, 512-520; Hayami, S. et al. Int. J. Cancer 2011, 128, 574-586; Schildhaus, H. U. et al. Hum. Pathol. 2011, 42, 1667-1675; Bennani-Baiti, I. M. et al. Hum. Pathol. 2012, 43, 1300-1307). Its over-expression correlates to tumor recurrence in prostate cancer (Kahl, P. et al. Cancer Res. 2006, 66, 11341-11347), and has a role in various differentiation processes, such as adipogenesis (Musri, M. M. et al. J. Biol. Chem. 2010, 285, 30034-30041), muscle skeletal differentiation (Choi, J. et al. Biochem. Biophys. Res. Commun. 2010, 401, 327-332), and hematopoiesis (Hu, X. et al. Proc. Natl. Acad. Sci. USA 2009, 106, 10141-10146; Li, Y. et al. Oncogene 2012, 31, 5007-18). KDM1A is further involved in the regulation of cellular energy expenditure (Hino S. Et al. Nat Commun. 2012, doi: 10.1038/ncomms1755), in the control of checkpoints of viral gene expression in productive and latent infections (Roizman, B. J. Virol. 2011, 85, 7474-7482) and more specifically in the control of herpes virus infection (Gu, H. J. Virol. 2009, 83, 4376-4385) and HIV transcription (Sakane, N. et al. PLoS Pathog. 2011, 7(8):e1002184). The role of KDM1A in the regulation of neural stem cell proliferation (Sun, G. et al. Mol. Cell Biol. 2010, 30, 1997-2005) as well as in the control of neuritis morphogenesis (Zibetti, C. et al. J. Neurosci. 2010, 30, 2521-2532) suggests its possible involvement in neurodegenerative diseases.
Furthermore, there are evidences of the relevance of KDM1A in the control of other important cellular processes, such as DNA methylation (Wang, J. et al. Nat. Genet. 2009, 41(1):125-129), cell proliferation (Scoumanne, A. et al. J. Biol. Chem. 2007, 282, 15471-15475; Cho, H. S. et al. Cancer Res. 2011, 71, 655-660), epithelial mesenchimal transition (Lin, T. et al. Oncogene. 2010, 29, 4896-4904) and chromosome segregation (Lv, S. et al. Eur. J. Cell Biol. 2010, 89, 557-563). Moreover, it was found that KDM1A inhibitors were able to reactivate silenced tumor suppressor genes (Huang, Y. et al. Proc. Natl. Acad. Sci. USA. 2007, 104, 8023-8028; Huang, Y. et al. Clin. Cancer Res. 2009, 15, 7217-7228), to target selectively cancer cells with pluripotent stem cell properties (Wang, J. et al. Cancer Res. 2011, 71, 7238-7249), as well as to reactivate the all-trans-retinoic acid differentiation pathway in acute myeloid leukemia (Schenk, T. et al. Nat Med. 2012, 18, 605-611).
The more recently discovered demethylase KDM1B (LSD2) displays—similarly to KDM1A—specificity for mono- and di-methylated Lys4 of histone H3. KDM1B, differently from KDM1A, does not bind CoREST and it has not been found up to now in any of KDM1A-containing protein complex (Karytinos, A. et al. J. Biol. Chem. 2009, 284, 17775-17782). On the contrary, KDM1B forms active complexes with euchromatic histone methyltransferases G9a and NSD3 as well as with cellular factors involved in transcription elongation. KDM1B has been reported to have a role as regulator of transcription elongation rather than that of a transcriptional repressor as proposed for KDM1A (Fang, R. et al. Mol. Cell 2010, 39, 222-233).
KDM1A and KDM1B are both flavo amino oxidase dependent proteins sharing a FAD coenzyme-binding motif, a SWIRM domain and an amine oxidase domain, all of which are integral to the enzymatic activity of KDM1 family members. Moreover, both KDM1A and KDM1B show a structural similarity with the monoamine oxidases MAO-A and MAO-B.
Indeed, tranylcypromine, a MAO inhibitor used as antidepressant agent, was found to be also able to inhibit LSD1. The compound acts as an irreversible inhibitor forming a covalent adduct with the FAD cofactor. (Lee, M. G. et al. Chem. Biol. 2006, 13, 563; Schmidt, D. M. Z. et al. Biochemistry 2007, 46, 4408).
The synthesis of tranylcypromine analogs and their LSD1 inhibitory activity has been described in Bioorg. Med. Chem. Lett. 2008, 18, 3047-3051, in Bioorg. Med. Chem. 2011, 19, 3709-3716, and in J. Am. Chem. Soc. 2011, 132, 6827-6833. Further arylcyclopropylamine and heteroarylcyclopropylamine derivatives as LSD1, MAO-A and/or MAO-B enzyme inhibitors are disclosed in US2010/324147, in WO2012/045883 and in WO2013/022047.
WO2011/131576 discloses tranylcyclopropylamine compounds of the general formula

wherein A is R or CH(R1)-NH—CO—R2; R and R2 are selected from: alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heteroaryl, heterocycloalkyl, cycloalkylalkyloxy, arylalkyloxy, heteroarylalkyloxy, heterocycloalkylalkyloxy, cycloalkylalkyl, arylalkyl, heteroarylalkyl, heterocycloalkylalkyl, cycloalkylalkylamino, arylalkylamino, heteroarylalkylamino, heterocycloalkylalkylamino; R1 is selected from: alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heteroaryl, heterocycloalkyl, cycloalkylalkyl, arylalkyl, heteroarylalkyl, heterocycloalkylalkyl; and R3 is H, lower alkyl.
However, there is still the need for compounds endowed with inhibitory activity on KDM1A and/or KDM1B enzyme activity with a low inhibitory activity on MAOA and/or MAOB enzymes.
MAOs are well known targets for the treatment of diseases of the central nervous system, such as depression or Parkinson's disease. However, inhibition of the MAOs are associated with side effects, among them tyramine-induced hypertensive crisis or the serotonin syndrome, which occurs in situation of concomitant use of MAO inhibitors 882; Iqbal, M. M. Ann Clin Psychiatry, 2012, 24, 310-318).